Telephone-exchange system.



PATENTED NOV. 21, 1905.

M. G. KELLOGG. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED DEG. 20, 1894 wmmkoz: .Jm 4.1622 4 bn ivioamnesubscribers lines.

UNITED STATES PATENT OFFICE.

MILO e. KELLOGGQOF CHICAGO, ILLINOIS.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented Nov. 21, 1905.

Application filed December 20, 1894. Serial No. 532,483.

In the accompanying drawings, Figure 1v shows a divided exchange systemand illustrates two divisions of boards with two boards in each divisionand the circuit connections and apparatus at the central oflice for twoswitching apparatus of the central-office operator; Fig. 3, thecentral-oflice-operators test devices, and Fig. 4 the organization atthe subscribers station.

Fig. lshows two divisions of boards (A and B) of two boards in eachdivision (A A and B B for two divisions of lines A and B. Each line hasa switch on each board of its division of boards and on one board of theother division of boards, according to my divided exchange system. Theswitches are represented at s s, &c. Each switch has two contact-pieces(marked 9 j) and a switch-hole (marked Z) adapted to receive a loopswitchplug, (marked D Din Fig. 2,) and when a plug is inserted into aswitch-hole its two contactpieces form connection with the twocontactpieces 9 and j of the switch, respectively. One side or branch ofa line is connected to one contact-piece of each switch of the line saypiece gand the other side or branch of the line is connected to theother contactpiece of each switch of the linesay j.

There are two annunciators for each line (marked w w) and tworetardation coils for each line, (marked it One side or branch of eachline is permanently grounded through one annunciator andretardation-coil of the line, and the other side or branch of the lineis permanently grounded through the other annunciator andretardation-coil of the line.

The two annunciators of a line are placed at two boards one at eachdivision of boards and at boards where the calls of the line are to beanswered.

Fig. 2 shows an operators cord system for an operator at any board. D Dare a pair of Fig. 2 shows the plug.

switch 8 at its board and when so placed to connect its contact-pieceswith the two contact-pieces g j of the switch, respectively.

The two contact-pieces of one plug are connected to the twocontact-pieces of the other plug, respectively, by two flexibleswitch-conductors. Each operator has as many pairs of plugs with cordsas she may need for her work.

Y is a looping-in switch for the pair of plugs shown, having twoswitch-levers and three pairs of contact-bolts on which the levers maybe alternately placed. The two levers of the switch are connected to thetwo flexible conductors, respectively, which connect the plugs.

23 is the operators telephone, and O is a testbattery. The telephone andbattery are in a loop which connectsa pair of the switch-bolts.

o is a clearing-out annunciator, and O is a test-battery. Thisannunciator and the battery are in a loop which connects another pair ofthe switch-bolts.

C is a callinggenerator in a loop, which connects the remaining pair ofswitch-bolts.

Each pair of plugs has a switch ,Y, a clearing-out annunciator o, and atest-battery O In the operators test system, T is a testplug, and t atest-receiving instrument. The plug is adapted to be placed for testinginto connection with any switch-contact g or j at its board and isgrounded through the test-receiving instrument. Each operator has a testsystem.

'In the subscribers station apparatus,(shown in Fig. 4,)1 is thetelephone-switch; 2, the subscribers telephone; 3, his signal-bell, and4 his calling-generator. a and b are two keys each having a pair ofcontacts normally open, but closed at the will of the subscriber. Thecircuits and connections are substantially as shown and may be such asare usual in subscribers station apparatus with the addition of theconnections of the keys, such as will be described.

When the telephone is on the switch, the signal-bell is in the circuitof the line and the telephone is short-circuited, so as to bepractically out of the circuit. When the telephone is off the switch, itis in the circuit of the line and the signal-bell is short-circuited, soas to be practically out of the circuit. The

armature of the calling-generator is in the loop-plugs, each adapted tobe placed in any IIO is grounded. The other point of key a is connectedto the line-circuit on one side of the generator-armature coil, and theother point of the key 6 is connected to the line-circuit on the otherside of the armature.

The subscribers station apparatus should preferably be connected intothe line-circuit, so that the generator is between key a and theannunciator of the line which is located in division A of boards and isbetween key 6 and the annunciator of the line which is located indivision B of boards.

The annunciators may all be of the ordinary kind of'nonpolarizedtelephone-annunciators.

The operation of the system is as follows: If a subscriber wishesconnection with a subscriber whose line is in division A, he presses onhis key a and operates his generator. A calling-current then goesthrough a circuit from the subscribers ground through the contacts ofkey a, the generator, one side or branch of the line, and to ground atthe central office through the annunciator located at one'of the boardsof division A. The annunciator will thereby indicate a call. The otherannunciator of the line will not indicate a call,

because the line is grounded between the; generator and the annunciatorby a circuit connection through key a of practically no resistance andthe annunciator is practically short-circuited. When the operator towhom the annunciator which indicates the call is assigned observes theindication, she places one of her switch-plugs D in the switch of theline, the levers of the switch Y being in position so that her telephonebridges or cross-connects the conductors of the plug, her telephone isin closed circuit with the line and she will receive the order of thesubscriber. This closed circuit is, say, from one side or branch of theline through the plug contact piece connected with it, to the flexibleconductor connected with the plug contact-piece, thence to theswitch-lever, thence through the telephone to the other switch-lever,thence to the other contact of the plug, and thence to the other side orbranch of the line. When the operator receives the order of thesubscriber, she tests the line wanted, as will hereinafter be indicated,and ifshe finds itto be free, or not in use, she places the other plugof the pair in the switch of the line. The two lines are then connectedtogether into a closed metallic circuit, and this circuit is bridged orcrossconnected by the operators telephone. This closed metallic circuitis, say, from one side or branch of one line to the contact-piece of theplug in its switch, thence through one of the flexible conductors to acontact-piece of the plug, which is in the switch of the other line,thence to one side or branch of the other line, thence through thecircuit of that line to the other contact-piece of the plug, which is inits switch, thence through the other flexible conductor to the othercontact-piece of the first-mentioned plug, and thence to the other sideor branch ofthe first-mentioned line. The operator may now move thelever of the looping-in switch Y, so that the calling-generator Bbridges the two sides of the closed metallic circuit, and acalling-current will pass over the metallic circuit to the line of thesubscriber wanted and ring his signal-bell. The operator will then movethe levers of the switch, so that the clearing-out annunciator o bridgesor cross-connects the closed metallic circuit of the two lines. Thesubscribers will then carry on their conversation. When the subscribersare through conversation, either may operate his calling-generatorwithout pressing on either of his keys at or b. A current will then passthrough his metallic circuit, which will operate the clearing-outannunciator in the central ofiice, which bridges pr connects the twosides or branches of his If the subscriber from whom the call hadoriginated had desired conversation with a subscriber whose line is indivision B, the operations would have been the same as those describedexcept that he would have pressed on key-b when he sent in his call.

When two lines are connected together into a closed metallic circuit forconversation, one side of the circuit is grounded at the central officethrough one annunciator and retarda tion-coil of each line and the otherside of the circuit is grounded through the other annunciator andretardation-coil of each line. high retardation and resistance of theseground connections or taps are, however, such as not to greatly affectthe telephone conversation between the subscribers.

It is evident that when a clearing-out signal is sent by eithersubscriber, as heretofore described, a portion of the generated currentwill divide so as to pass through the line-annunciators of the twolines. On account of the high resistance of the circuits through theannunciators the amount of current which passes through them will not besuflicient to operate them. The circuit through the clearing-outannunciator will be of much less resistance, and consequently much morecurrent will pass through it and sufficient to operate it. The strengthof the generator and the resistances of the circuits and apparatus andthe sensitiveness of the annunciators can be readily adjusted to eachother in such a manner that when a call is sent in by a subscriber itwill operate the annunciator he intends and will not operate his otherannunciator, and when a clearing-out current is sent by eithersubscriber it will operate the clearing-out annunciator and will notoperate either of the lineannunciators.

Should any subscriber attempt to send a call for a connection bypressing either of his keys and operating his calling-generator whilehis line is already switched for conversation, as

The

together.

may be the case when the subscribers neglect to send a clearing'outsignal when they are line-annunciators, and part of the current willalso pass through the line-annunciators of the other subscriber if thetwo lines are connected The greater portion of the current will,however, pass through the clearing-out annunciator. The strength of thegenerators and the resistances of the circuits and apparatus andthesensitivencss of the annunciator-s can be readily and should beadjusted to each other in such a manner that when a call is sent -in bya subscriber and his line is already switched enough of the current willnot pass through any of the line-annunciators to operate them; butsufiicient current will pass through the clearing-out annunciator tooperate it. When the operator moves the levers of his switch Y so as toconnect her callinggenerator B into circuit, the generator is bridgedbetween the two sides of the combined circuit of the two lines, and thecurrent di vides, according to the well-known law of the distribution ofcurrents in derived circuits, so that the greater part of the currentpasses in two derived circuits to the two subscribers stations,respectively, and operates their call- -known modifications of theoperators switches the line from which the call originates may bedisconnected from the generator while the operator sends thecalling-current, and in that case the current will only go over theline' and through the annunciators of the subscriber wanted. In eithercase the strength of the operators generator and the resistances of thecircuits and apparatus and the sensi- -tiveness of the bells and theannunciators can be readily and should be adjusted to each other in sucha manner that when a call is sent by the operator the line-annunciatorswill'not be operated, while the subscribers bells (or the subscribersbell, as the case may be) will be rung by the current. The system may bemodified-as, for instance, for multiple switchboard systems, which donot contain the divided-exchange featu re by leaving out the annunciatorwith its ground connection, which is connected to one side or branch ofthe line. In that case the key of the subscribers station, which is tobe depressed to operate this annunciator, may be left out. Theline-annunciators, as well as the clearingout annunciator, will be inclosed circuit with the generator when the clearing-out signal is 'sent,and in all cases the strength of the ourrent and the resistances of theline-annunciator circuits should be so great as compared withthereslstance-of the clearing-out annunof the line.

ciator-circuit that when the clearing-out current passes through themthe line-annunciator will not be operated.

The system of switching and operation which I have herein described maybe modified so as to prevent in other ways the lineannunciators from.being operated while the line is switched and either a subscriber or anoperator sends a calling-current over the line.

The test system is as follows: When a line is switched for conversation,it has a test-battery, either the battery 0 in the loop with theoperators telephone or the battery G in the loop with the clearing-outannunciator, in a bridge or cross connection to the two sides When,therefore, an operator at any board places her test-plugT into contactwith any contact-piece g or 1' of a line and the line is switched forconversation, a complete circuit is established which contains hertestreceiving instrument and a test-battery, and the instrument willsound or respond, indicating that the line is switched for use. Thecomplete circuit is, say, from ground through the test receivinginstrument to the testplug, thence to the switch-contact connected withone side of the line to which the plug is applied, thence to theswitch-contact of the line at which the line is switched, thence throughthe test-battery, which bridges the circuit to the other side of theline, and thence to ground through the annunciator and retardation-coil,through which the last-mentioned side of the line is grounded.

When a line is not switched for conversation, there is no completecircuit established on testing which contains the operatorstestreceiving instrument and a battery, and the instrument will notsound. The operator can therefore determine by testing whether or notany line connected to her board is switched for conversation.

Instead of the annunciator and retardationcoil for each line anannunciator of high resistance and retardation to telephone-currents maybe used.

Other systems of testing than that shown and described may be used inconnection with the calling and switching system I have described.

I claim as my invention-- 1. In a telephone-exchange system, themetallic-circuit lines divided into two divisions, the multipleswitchboards, divided into two divisions, one division of boards foreach division of lines; switches for each of said lines, oneswitch foreach line on each of the several boards of its division, and on oneboard of the other division; two annunciators at the central oflice foreach line, through one of which one side or branch of the line ispermanently grounded and through the other of which the other side orbranch of the line is permanently grounded; in combination with acalling-generator at each subscribers station permanently or wheneveroperated to send a call in the through or closed circuit of the line atsaid station, and contacts to at will ground his line on either side ofsaid generator.

2. In a telephone-exchange system, the metallic-circuit lines dividedinto two divisions, the multiple switchboards divided into twodivisions, one division of boards for each division of lines, switchesfor saidlines, one switch for each line on each board of its divisionand on one board only of the other division, each switch having twocontactpieces, one branch of each line being connected to one of thecontact-pieces of each switch of the line and the other branch of theline being connected to the other contact-piece of each switch of theline, in combination with two permanent ground connections at thecentral office for each line, two annunciators for each line, one ineach of the ground connections and at a board in each division of boardsand Where the line has a switch, pairs of loop switch-plugs at eachboard, the two contacts of each plug being connected by flexibleconductor-circuits to the two contacts of its mate, respectively, eachplug being adapted to be inserted into each switch at its board and wheninserted to form contact between its two contacts and the twocontact-pieces of the switch, respectively, a calling-generator at eachsubscribers station permanently or whenever operated to send a call inthe through or closed circuit of the line at said station, and contactsat each subscribers station to at will ground the line on either side ofthe generator.

3. In a telephone-exchange system, the metallic-circuit lines dividedinto two divisions, the multiple switchboards divided into twodivisions. one division of boards for each division of lines, switchesfor said lines, one switch for each line on each board of its divisionand on one board only of the other division, each switch having twocontact-pieces, one branch of each line being connected to one of thecontact-pieces of each switch of the line and the other branch of theline being connected to the other contact-piece of each switch of theline, in combination with two permanent ground connections at thecentral office for each line, two annunciators for each line, one ineach of the ground connections and at a board in each division of boardsand where the line has a switch, pairs of loop SWltClP send a call inthe through or closed circuit of the line at said station, and contactsat each subscribers station to at will ground the line on either side ofthe generator.

4. In a telephoneexchange system, a metallic-circuit line extending fromits subscribers station to the central oflice, and two annunciators atthe central oflice for such line, through one of which one side orbranch of the line is permanently grounded, and through the other ofwhich the other side or branch of the line is permanently grounded, incombination with a calling-generator permanently or whenever operated tosend a call in the through or closed circuit of the line at thesubscribers station and two keys there, each with a pair of contactsnormally open but closed at the will of the subscriber, one contact ofeach key being grounded and the other two contacts of the keys beingconnected to the line-circuit, one on one side and the other on theother side of the generator.

5. In a telephone-exchange system,metalliccircuit lines extending fromthe subscribers station to the central oflice, and two annunciators atthe central office for each line, through one of which one side orbranch of the line is grounded and through the other of which the otherside or branch of the line is grounded, in combination with acalling-generator permanently or whenever operated to send acall in thethrough or closed circuitof the line at the subscribers station, twokeys there, each with a pair of contacts normally open but closed at thewill of the subscriber, one contact of each key being grounded .and theother two contacts of the keys being permanently connected to theline-circuit, one on one side and the other on the other side of thegenerator, and switching apparatus at the central oflice to connecttogether any two of the lines into a metallic circuit which does notcontain the line-annunciator.

6. In a telephone-exchange system, two metallic-circuit linestemporarily connected together into a closed metallic circuit forconversation, and two annunciators for each line, through which,respectively, the two sides of said metallic circuit are grounded infour ground connections, two from each side of the circuit, incombination with a clearingout annunciator in a bridge orcross-connecting circuit to said closed metallic circuit, and

a calling-generator operated in said circuit at either subscribersstation to send a clearingout signal, the strength of thegenerator, theresistances of the various apparatus, and circuits, and thesensitiveness of the annunciators being such that when the generator isthus operated, the line-annunciators will not be operated while theclearing-out annunciator will be operated by the current passing throughthem.

7. In a telephone-exchange system, two metallic-circuit linestemporarily connected together into a closed metallic circuit forconversation, and two annunciators for each line, through which,respectively, the two sides of said metallic circuit are grounded infour ground connections, two from each side of the circuit, incombination with a clearingout annunciator in a bridgeorcross-connecting circuit to said closed metallic circuit, and acalling-generator operated in said oircuit'at either subscribers stationto send a clearingout signal, said line-annunciators not being operatedbut said clearing-out annunciator being operated by the currentgenerated.

8. In atelephone-exchange system, two metallic-circuit lines temporarilyconnected together into a closed metallic circuit for conversation, andfour annunciators through which, respectively, the two sides of saidmetallic circuit are grounded in four ground connections, two from eachside of the circuit, in combination with a clearing-out annunciator in abridge or cross-connecting circuit to said closed metallic circuit, anda calling-generator operated in said circuit at either subscribersstation to send a clearing out signal, the strength of the generator,the resistances of the various apparatus and circuits, and thesensitiveness of the annunciators being such that when the generator isthus operated, the line-annunciators will not be operated while theclearing-out annunciator will be operated by the current passing throughthem.

9. In a telephone-exchange system, two metallic-circuit linestemporarily connected together into a closed metallic circuit forconversation, and four annunciators through which, respectively, the twosides of said metallic circuit are grounded in four ground connections,two from each side of the circuit, .in combination with a clearing-outannunciator in a bridge or cross-connecting circuit to said closedmetallic circuit, and a calling-generator operated in said circuit ateither subscribers station to send a clearing-out signal, saidlineannunciators not being operated, but said clearing-out annunciatorbeing operated by the current generated.

10. In a telephone-exchange system,two metallic-circuit linestemporarily connected together into a closed metallic circuit forconversation, and two annunciators for each line, through which,respectively, the two sides of said metallic circuit are grounded infour ground connections, two from each side of the circuit, incombination with a clearing-out annunciator, in abridge orcross-connecting circuit to said closed metallic circuit, acalling-generator operated in said circuit at either subscribers stationand a key then operating to ground said circuit at said station on oneside of said generator, the strength of the generator, the resistancesof the various apparatus and circuits, and the sensitiveness of theannunciators being such that when the generator is thus operated, theline-annunciators will not be operated while the clearingout annunciatorwill be operated by the current passing through them.

11. In atelephone-exchange system,twometallic-circuit lines temporarilyconnected together into a closed metallic circuit for conversation, andtwo annunciators for each line, through which, respectively the twosides of said metallic circuit are grounded in four ground connections,two from each side of the circuit,.in combination with a clearingoutannunciator in a bridge or cross-connecting circuit to said closedmetallic circuit, a calling-generator operated in said circuit at eithersubscribers station and a key then operating to ground said circuit atsaid station on one side of said generator, said line-annunciators notbeing operated but said clearing-out annunciator being operated by thecurrent generated.

12. In atelephone-exchange system,two metallic-circuit lines temporarilyconnected together into a closed metallic circuit for conversation, andtwo annunciators, through which, respectively, the two sides of saidmetallic circuit are grounded, in combination with a clearing-outannunciator in a bridge or crossconnecting circuit to said closedmetallic circuit, a calling-generator operated in said closed metalliccircuit at either subscribers station and a key then or while thegenerator is thus being operated in said closed metallic circuitoperating to ground said circuit at said station on one side of saidgenerator, said line-annunciators not being operated but saidclearing-out annunciator being operated by the current generated.

13. In a telephone-exchange system,two metallic-circuit linestemporarily connected together into a closed metallic circuit forconversation and a line-annunciator through which one side of saidmetallic circuit is then grounded in combination with a clearing-outannunciator in a bridge or cross-connecting circuit to said closedmetallic circuit, a calling-generator operated in said closed metalliccircuit at either subscribers station to send a clearing-out signal, anda key then or while the generator is thus being operated in said closedmetallic circuit operating to ground said circuit at said station on oneside of said generator and with said generator between said groundconnection thus established and said annunciator, the strength of thegenerator, the resistances of the various apparatus and circuits, andthe sensitiveness of the annunciators being such that when the generatoris thus operated the line-annunciator will not be operated, while theclearing-out annunciator will be operated by the current passing throughthem.

14:. In a telephone-exchange system,two metallic-circuit linestemporarily connected together into a closed metallic circuit forconversation and a line-annunciator through which one side of saidmetallic circuit is then grounded, in combination with a clearing-outannunciator in a bridge or cross-connecting circuit to said closedmetallic circuit, a calling-generator operated in said closed metalliccircuit at either subscribers station to send a clearing-out signal, anda key then or while the generator is thus being operated in said closedmetallic circuit operating to ground said circuit at said station on oneside of said generator and with said generator between said groundconnection thus established and said annunciator, said line-annunciatornot being operated but said clearing-out annuncialor being operated bythe current generate In testimony whereof I have hereunto subscribed myname.

MILO G. KELLOGG. Witnesses:

H. M. WALKER, E S. WALKER.

